Most economic valuation studies of species derive from stated preferences methods. These methods fail to take into account biodiversity values that the general public is not (made) informed about or has no experience with. Hence, production function (PF) and replacement cost (RC) approaches to valuation may be preferable in situations where species perform key life support functions in ecosystems, such as seed dispersal, pollination, or pest regulation. We conduct an RC analysis of the seed dispersal service performed by the Eurasian jay (Garrulus glandarius) in the Stockholm National Urban Park, Sweden. The park holds one of the largest populations of giant oaks in Europe, and the oak (Quercus robur and Quercus petrea) represents a keystone species in the hemiboreal forests. The primary objective was to estimate the number of seed-dispersed oak trees that resulted from jays and to determine the costs of replacing this service though human means. Results show that depending upon seeding or planting technique chosen, the RC per pair of jays in the park is SEK 35,000 (USD 4900) and SEK 160,000 (USD 22,500), respectively. Based on the park's aggregated oak forest-area, average RC for natural oak forest regeneration by jays is SEK 15,000 (USD 2100) to SEK 67,000 (USD 9400) per hectare, respectively. These estimates help motivating investments in management strategies that secure critical breeding and foraging habitats of jays, including coniferous forests and jay movement corridors. The analysis also illustrates the need for detailed ecological-economic knowledge in a PF or RC analysis. The continuous temporal and spatial oak dispersal service provided by jays holds several benefits compared to a man-made replacement of this service. PF and RC approaches are particularly motivated in cases of known functional ecological relationships, and critically important in estimating management measures where mobile link organisms and keystone species form key mutual relationships that generate high biodiversity benefits. In relation to obtained results, we discuss insights for conducting valuation studies on particular species.